Increased transcriptional activities of transforming growth factor beta receptors in scleroderma fibroblasts

The Role of Autophagy and Apoptosis in Affected Skin and Lungs in Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a complex autoimmune inflammatory disorder with multiple organ involvement. Skin changes present the hallmark of SSc and coincide with poor prognosis. Interstitial lung diseases (ILD) are the most widely reported complications in SSc patients and the primary cause of death. It has been proposed that the processes of autophagy and apoptosis could play a significant role in the pathogenesis and clinical course of different autoimmune diseases, and accordingly in SSc. In this manuscript, we review the current knowledge of autophagy and apoptosis processes in the skin and lungs of patients with SSc. Profiling of markers involved in these processes in skin cells can be useful to recognize the stage of fibrosis and can be used in the clinical stratification of patients. Furthermore, the knowledge of the molecular mechanisms underlying these processes enables the repurposing of already known drugs and the development of new biological therapeutics that aim to reverse fibrosis by promoting apoptosis and regulate autophagy in personalized treatment approach. In SSc-ILD patients, the molecular signature of the lung tissues of each patient could be a distinctive criterion in order to establish the correct lung pattern, which directly impacts the course and prognosis of the disease. In this case, resolving the role of tissue-specific markers, which could be detected in the circulation using sensitive molecular methods, would be an important step toward development of non-invasive diagnostic procedures that enable early and precise diagnosis and preventing the high mortality of this rare disease.

TDAG51 induces renal interstitial fibrosis through modulation of TGF-β receptor 1 in chronic kidney disease

Chronic kidney disease (CKD) is characterized by the gradual loss of renal function and is a major public health concern. Risk factors for CKD include hypertension and proteinuria, both of which are associated with endoplasmic reticulum (ER) stress. ER stress-induced TDAG51 protein expression is increased at an early time point in mice with CKD. Based on these findings, wild-type and TDAG51 knock-out (TDKO) mice were used in an angiotensin II/deoxycorticosterone acetate/salt model of CKD. Both wild-type and TDKO mice developed hypertension, increased proteinuria and albuminuria, glomerular injury, and tubular damage. However, TDKO mice were protected from apoptosis and renal interstitial fibrosis. Human proximal tubular cells were used to demonstrate that TDAG51 expression induces apoptosis through a CHOP-dependent mechanism. Further, a mouse model of intrinsic acute kidney injury demonstrated that CHOP is required for ER stress-mediated apoptosis. Renal fibroblasts were used to demonstrate that TGF-β induces collagen production through an IRE1-dependent mechanism; cells treated with a TGF-β receptor 1 inhibitor prevented XBP1 splicing, a downstream consequence of IRE1 activation. Interestingly, TDKO mice express significantly less TGF-β receptor 1, thus, preventing TGF-β-mediated XBP1 splicing. In conclusion, TDAG51 induces apoptosis in the kidney through a CHOP-dependent mechanism, while contributing to renal interstitial fibrosis through a TGF-β-IRE1-XBP1 pathway.

Effect of UVA1 on hypertrophic scarring in the rabbit ear model

Hypertrophic scars (HTSs) are common and cause functional and psychological morbidity. UVA1 (340-400 nm) phototherapy has been previously shown to be effective in the treatment of localized scleroderma, systemic sclerosis, and POEMS syndrome with minimal side effects, all of which are presented as collagen fibrils hyperplasia that is common with scarring in skin histology. In the present study, we aimed to investigate the impact of UVA1 on the protein expression of TGF-β signal pathway and myofibroblasts in a rabbit model of cutaneous scarring. Full-thickness skin wounds (2 cm × 5 cm in diameter) were made in New Zealand white rabbits to establish the hypertrophic scarring model. New Zealand white rabbits were divided into two treatment groups (n=30 wounds per group with an equal number of controls): medium-dose of UVA1 phototherapy group: 60 J/cm2; high-dose of UVA1 phototherapy group: 110 J/cm2. Left ears were used for treatment and the right ones were used for control. Treatment was administered five times weekly for 6 weeks. Treated and untreated control wounds were harvested at various time points and examined by histologic examination, immunohistochemical assessment, and ultrastructural evaluation. The results showed that UVA1 phototherapy caused a significant reduction in dermal thickness by histological features, whereas the scar index was descended significantly in both medium- and high-dose UVA1 groups compared with the control group. Examination of immunohistochemistry also revealed a marked suppression of tissue growth factor-β (TGF-β) (both medium- and high-dose), α smooth muscle actin (α-SMA) (only high-dose), and tissue inhibitor of metalloproteinase 1 (TIMP-1) (only high-dose), and apparent increase in matrix metalloproteinases (MMP-1) (both medium- and high-dose) compared with the control. The ultrastructural evaluation showed the collagen fibers' diameter had shrunk, and that fibroblastic cytoplasm was not affluent and in a quiescent stage. These findings of the present study suggested that administration of UVA1 irradiation is effective to improve the experimental HTS model and raises a possibility of the therapeutic approach of UVA1 in the scar. Although not directly examined in the present study, MMP inhibition is hypothesized to be responsible for this effect. However, early UVA1 treatment could not prevent the formation of scar model.

Parvovirus B19 activates in vitro normal human dermal fibroblasts: a possible implication in skin fibrosis and systemic sclerosis

OBJECTIVE

Fibrosis is the most characteristic pathological hallmark of SSc, a connective tissue disease characterized by vascular and immunological abnormalities, inflammation and enhanced extracellular matrix production, leading to progressive fibrosis of skin and internal organs. We previously demonstrated that parvovirus B19 (B19V) can infect normal human dermal fibroblasts (NHDFs) and that B19V persists in SSc fibroblasts. In this study, we investigated whether parvovirus B19V is able to activate in vitro NHDFs and to induce in these cells some phenotypic features similar to that observed in the SSc fibroblasts.

METHODS

We preliminarily analysed the time course of B19V infection in cultured NHDFs, then we investigated the ability of B19V to induce cell migration, invasive phenotype and mRNA expression of some profibrotic and/or proinflammatory genes.

RESULTS

We confirmed our previous findings that B19V infects NHDFs, but the infection is not productive. After incubation with B19V, NHDFs showed a significant increase of both migration and invasiveness, along with mRNA expression of different profibrotic genes (α-SMA, EDN-1, IL-6, TGF-β1 receptors 1 and 2, Col1α2), some genes associated with inflammasome platform (AIM2, IFI16, IL-1β, CASP-1) and genes for metalloprotease (MMP 2, 9 and 12).

CONCLUSION

These data suggest that B19V can activate dermal fibroblasts and may have a role in the pathogenesis of fibrosis. B19V-induced fibroblast migration and invasiveness could be due to the B19V-associated MMP9 overexpression and activation. Moreover, the up-regulation of MMP12, typical of SSc, could link the B19V infection of fibroblasts to the anti-angiogenic process.

Safer approaches to therapeutic modulation of TGF-β signaling for respiratory disease

The transforming growth factor (TGF)-β cytokines play a central role in development and progression of chronic respiratory diseases. TGF-β overexpression in chronic inflammation, remodeling, fibrotic process and susceptibility to viral infection is established in the most prevalent chronic respiratory diseases including asthma, COPD, lung cancer and idiopathic pulmonary fibrosis. Despite the overwhelming burden of respiratory diseases in the world, new pharmacological therapies have been limited in impact. Although TGF-β inhibition as a therapeutic strategy carries great expectations, the constraints in avoiding compromising the beneficial pleiotropic effects of TGF-β, including the anti-proliferative and immune suppressive effects, have limited the development of effective pharmacological modulators. In this review, we focus on the pathways subserving deleterious and beneficial TGF-β effects to identify strategies for selective modulation of more distal signaling pathways that may result in agents with improved safety/efficacy profiles. Adverse effects of TGF-β inhibitors in respiratory clinical trials are comprehensively reviewed, including those of the marketed TGF-β modulators, pirfenidone and nintedanib. Precise modulation of TGF-β signaling may result in new safer therapies for chronic respiratory diseases.

Sirtuin 3 Deregulation Promotes Pulmonary Fibrosis

Oxidative stress leads to alveolar epithelial cell injury and fibroblast-myofibroblast differentiation (FMD), key events in the pathobiology of pulmonary fibrosis (PF). Sirtuin 3 (SIRT3) is a mitochondrial protein deacetylase regulator of antioxidant response and mitochondrial homeostasis. Here, we demonstrate reduced SIRT3 expression in the lungs of old mice compared to young mice, as well as in two murine models of PF. The analysis of the pattern of SIRT3 expression in the lungs of patients with PF revealed low SIRT3 staining within the fibrotic regions. We also demonstrated, using murine models of PF and human lung fibroblasts, that reduced SIRT3 expression in response to transforming growth factor beta 1 (TGFβ1) promotes acetylation (inactivation) of major oxidative stress response regulators, such as SOD2 and isocitrate dehydrogenase 2. Reduction of SIRT3 in human lung fibroblasts promoted FMD. By contrast, overexpression of SIRT3 attenuated TGFβ1-mediated FMD and significantly reduced the levels of SMAD family member 3 (SMAD3). Resveratrol induced SIRT3 expression and ameliorated acetylation changes induced by TGFβ1. We demonstrated that SIRT3-deficient mice are more susceptible to PF compared to control mice, and concomitantly exhibit enhanced SMAD3 expression. Collectively, these data define a SIRT3/TGFβ1 interaction during aging that may play a significant role in the pathobiology of PF.

Chitinase 1 is a biomarker for and therapeutic target in scleroderma-associated interstitial lung disease that augments TGF-β1 signaling

Interstitial lung disease (ILD) with pulmonary fibrosis is an important manifestation in systemic sclerosis (SSc, scleroderma) where it portends a poor prognosis. However, biomarkers that predict the development and or severity of SSc-ILD have not been validated, and the pathogenetic mechanisms that engender this pulmonary response are poorly understood. In this study, we demonstrate in two different patient cohorts that the levels of chitotriosidase (Chit1) bioactivity and protein are significantly increased in the circulation and lungs of SSc patients compared with demographically matched controls. We also demonstrate that, compared with patients without lung involvement, patients with ILD show high levels of circulating Chit1 activity that correlate with disease severity. Murine modeling shows that in comparison with wild-type mice, bleomycin-induced pulmonary fibrosis was significantly reduced in Chit1⁻/⁻ mice and significantly enhanced in lungs from Chit1 overexpressing transgenic animals. In vitro studies also demonstrated that Chit1 interacts with TGF-β1 to augment fibroblast TGF-β receptors 1 and 2 expression and TGF-β-induced Smad and MAPK/ERK activation. These studies indicate that Chit1 is potential biomarker for ILD in SSc and a therapeutic target in SSc-associated lung fibrosis and demonstrate that Chit1 augments TGF-β1 effects by increasing receptor expression and canonical and noncanonical TGF-β1 signaling.

CD4+CD25+ regulatory T cells in systemic sclerosis and other rheumatic diseases

Systemic sclerosis (SSc) is a generalized connective tissue disorder, characterized by a wide spectrum of microvascular and immunological abnormalities, leading to a progressive thickening and fibrosis of the skin and other organs, such as the lungs, GI tract, heart and kidneys. SSc is thought to be an autoimmune disease owing to the presence of high affinity antibodies and possible clinical overlap with other autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. Autoimmune diseases arise because of a breakdown in immunological self tolerance. Self tolerance is maintained via multiple regulatory mechanisms within the immune system, including the thymic deletion of self-reactive T cells and mechanisms of peripheral tolerance. In recent years, the presence of CD4(+)CD25(+)FOXP3(+) Tregs has been identified as a major mechanism of peripheral tolerance, and accumulating evidence indicates that alterations in Treg frequencies and/or function may contribute to autoimmune diseases. Here, we will review recent data on the percentage, function and phenotype of CD4(+)CD25(+) Tregs in rheumatic disease, and discuss how recent developments may guide research in this area in SSc.

Activation of the activin A-ALK-Smad pathway in systemic sclerosis

Systemic sclerosis (SSc) is a chronic disease of unknown etiology that is characterized by multiple tissue fibrosis. Transforming Growth Factor-beta (TGF-β) is thought to be the most important mediator that induces fibrosis. However, the molecular mechanisms by which fibrosis is induced have not been fully elucidated. In this study, the role of activin, a member of the TGF-β superfamily, was investigated in the pathogenesis of fibrosis in SSc. Serum activin A levels in patients with SSc were measured by ELISA, and the expression of the activin receptor type IB (ACVRIB/ALK4) and the activity of the signaling pathway via ACVRIB/ALK4 were investigated using western blotting. To evaluate a potential therapeutic strategy for SSc, we also attenuated the ACVRIB/ALK4 pathway using an inhibitor. Serum activin A levels were significantly higher in SSc patients than in normal controls. Activin A and ACVRIB/ALK4 expression were also higher in cultured SSc fibroblasts. Activin A stimulation induced phosphorylation of Smad2/3 and CTGF expression in SSc fibroblasts. Procollagen production and Col1α mRNA also increased upon stimulation by activin A. The basal level of Smad2/3 phosphorylation was higher in cultured SSc fibroblasts than in control cells, and treatment with the ALK4/5 inhibitor SB431542 prevented phosphorylation of Smad2/3 and CTGF expression. Furthermore, production of collagen was also induced by activin A. Activin A-ACVRIB/ALK4-Smad-dependent collagen production was augmented in SSc fibroblasts, suggesting the involvement of this signaling mechanism in SSc. Inhibition of the activin A-ACVRIB/ALK4-Smad pathway would be a new approach for the treatment of SSc.

Autoimmune mechanisms of scleroderma and a role of oxidative stress

Scleroderma is a fibrotic condition characterized by immunological abnormalities, vascular injury and increased accumulation of extracellular matrix proteins in the skin. Although the etiology of scleroderma has not yet been fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts via a number of mediators, such as cytokines, chemokines and growth factors. Recent investigations have further suggested that reactive oxygen species (ROS) are involved and play a role of autoimmunology in scleroderma. In this review, current findings on the autoimmune mechanisms in the pathophysiology of scleroderma are described.

Autocrine transforming growth factor β signaling regulates extracellular signal-regulated kinase 1/2 phosphorylation via modulation of protein phosphatase 2A expression in scleroderma fibroblasts

BACKGROUND

During scleroderma (SSc) pathogenesis, fibroblasts acquire an activated phenotype characterized by enhanced production of extracellular matrix (ECM) and constitutive activation of several major signaling pathways including extracellular signal-related kinase (ERK1/2). Several studies have addressed the role of ERK1/2 in SSc fibrosis however the mechanism of its prolonged activation in SSc fibroblasts is still unknown. Protein phosphatase 2A (PP2A) is a key serine threonine phosphatase responsible for dephosphorylation of a wide array of signaling molecules. Recently published microarray data from cultured SSc fibroblasts suggests that the catalytic subunit (C-subunit) of PP2A is downregulated in SSc. In this study we examined the role and regulation of PP2A in SSc fibroblasts in the context of ERK1/2 phosphorylation and matrix production.

RESULTS

We show for the first time that PP2A mRNA and protein expression are significantly reduced in SSc fibroblasts and correlate with an increase in ERK1/2 phosphorylation and collagen expression. Furthermore, transforming growth factor β (TGFβ), a major profibrotic cytokine implicated in SSc fibrosis, downregulates PP2A expression in healthy fibroblasts. PP2A-specific small interfering RNA (siRNA) was utilized to confirm the role of PP2A in ERK1/2 dephosphorylation in dermal fibroblasts. Accordingly, blockade of autocrine TGFβ signaling in SSc fibroblasts using soluble recombinant TGFβ receptor II (SRII) restored PP2A levels and decreased ERK1/2 phosphorylation and collagen expression. In addition, we observed that inhibition of ERK1/2 in SSc fibroblasts increased PP2A expression suggesting that ERK1/2 phosphorylation also contributes to maintaining low levels of PP2A, leading to an even further amplification of ERK1/2 phosphorylation.

CONCLUSIONS

Taken together, these studies suggest that decreased PP2A levels in SSc is a result of constitutively activated autocrine TGFβ signaling and could contribute to enhanced phosphorylation of ERK1/2 and matrix production in SSc fibroblasts.

[Cytokines and T cell differentiation in systemic sclerosis]

The physiopathology of systemic sclerosis remains unclear within a complex interaction between vasculopathy, perivascular inflammatory infiltrate, extensive tissue fibrosis and auto-immune manifestations. Chronology between vascular disease and adjacent inflammatory cell infiltration is still not yet clarified. There is growing evidence that T cell activation and its cytokine expression play a key role in vascular impairment occurrence and collagen dysregulation. Nevertheless, cytokine descriptions are mainly limited to blood and tissue measurement and the T cells differentiation analysis restricted to the Th1/Th2 balance. The purpose of this review is to establish an exhaustive cartography of cytokines involved in T cell differentiation, regarding the recent advance in T lymphocyte differentiation, including Th9, Th17, Th22 and regulatory T cells (Treg) pathways. This review will focus on Th17, Th22 and Treg differentiation, corresponding to the equilibrium between inflammation and tolerance. Finally, regarding published results in systemic sclerosis, T cells participation appears to be more a Th1/Th2 co-expression than an exclusive Th1 or Th2 polarization. Also, a possible Th22/Treg imbalance is suggested, leading to a Th22 overexpression and likely to tissue inflammation genesis.

Akt blockade downregulates collagen and upregulates MMP1 in human dermal fibroblasts

Acutely transforming retrovirus AKT8 in rodent T-cell lymphoma (Akt) is a serine/threonine kinase that plays important roles in survival, cell-cycle progression, and cell proliferation, and has recently been implicated in collagen regulation. The aim of this study was to determine the role of Akt in collagen deposition by normal dermal fibroblasts, and to determine the sensitivity of cultured systemic sclerosis (SSc) fibroblasts to Akt inhibition. We show that blockade of Akt using pharmacological inhibitors, small interfering RNA (siRNA), and a dominant-negative Akt mutant led to inhibition of the basal type I collagen production. Furthermore, inhibition of Akt upregulated basal matrix metalloproteinase 1 (MMP1) production and reversed the inhibitory effect of transforming growth factor-beta (TGF-beta) on MMP1 gene expression. In addition, SSc fibroblasts were more sensitive to Akt inhibition, with respect to collagen and MMP1 production. These findings suggest that in human dermal fibroblasts, Akt has dual profibrotic effects, increasing collagen synthesis and decreasing its degradation via downregulation of MMP1. Akt could directly contribute to elevated collagen in SSc fibroblasts and it may represent an attractive target for therapy of SSc fibrosis.

Fibrosis in systemic sclerosis

This article reviews current understanding of the pathophysiology of fibrosis in systemic sclerosis. It highlights recent discoveries, insights, and emerging research, and potential opportunities for the development of targeted antifibrotic therapies.

The immunobiology of systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is a chronic connective tissue disease characterized by vascular damage, autoimmunity, and excessive collagen deposition. Despite advances in disease-specific treatment of other rheumatologic diseases, disease-targeted treatment in SSc continues to be elusive. In this review, our goal was to place the contemporary immunobiology of SSc in the perspective of clinical medicine.

METHODS

We performed a PubMed search for the period from 1989 to 2007, using the keyword, "systemic sclerosis," resulting in a total of 9099 publications, including 1252 reviews. Articles were then selected based on their discussion of recent advances in the elusive pathogenesis of SSc. A final total of 259 articles were chosen for the review.

RESULTS

The SSc hallmarks of vascular damage, immunologic activation, and collagen deposition can be traced to 4 major factors: T-cells, fibroblasts, B-cells, and cytokines/chemokines. T-cells are a major component of the infiltrate in skin and lung, exhibiting increased expression of activation markers and showing signs of antigen-driven expansion. Preliminary data indicate that induction of oral tolerance with collagen, a target of SSc T-cell responses, is associated with clinical benefits. Although this suggests that T-cells participate in the pathogenesis of SSc, their precise role and antigen specificity largely remain to be elucidated. Defective numbers and functions of certain T-cell subsets, such as natural killer and gammadelta T-cells, may be involved in the failure to maintain tolerance. Other data suggest that gammadelta T-cells may themselves be effector cells in endothelial cell cytotoxicity. There are several lines of evidence for a pathogenic role of B-cells in SSc, in particular, through the production of autoantibodies. Antibody-dependent cell-mediated cytotoxicity is a primary pathogenic event in an animal model of SSc and is likely to be involved in human SSc. Nonetheless, there is as yet no convincing evidence for the pathogenicity of SSc-specific antibodies. SSc fibroblasts exhibit a specific phenotype characterized not only by excessive collagen production but also by increased responsiveness to and production of cytokines and chemokines. This phenotype is induced by a complex network of cytokines and chemokines but appears to be maintained in the absence of exogenous stimuli via the autocrine production of some of these factors by SSc fibroblasts themselves, particularly transforming growth factor, platelet-derived growth factor, monocyte chemoattractant protein 1, and interleukin-1.

CONCLUSIONS

Significant variations in laboratory data among patients suggest that the pathology reflects a heterogeneous disease. Nonetheless, the possibility of achieving clinical benefits by inducing oral tolerance highlights the importance of characterizing SSc T-cell antigens. It is hoped that the identification of some of the key players in the induction and maintenance of the SSc fibroblast phenotype may yield new disease-targeted treatment regimens for patients with SSc.

Autocrine TGF-beta signaling in the pathogenesis of systemic sclerosis

Excessive extracellular matrix deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). Fibroblasts isolated from sclerotic lesions in patients with SSc and cultured in vitro are characterized by increased synthesis of collagen and other extracellular matrix components, consistent with the disease phenotype. Thus, cultured scleroderma fibroblasts serve as a principal experimental model for studying the mechanisms involved in extracellular matrix overproduction in SSc. The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that transforming growth factor-beta (TGF-beta) is a key mediator of tissue fibrosis as a consequence of extracellular matrix accumulation in the pathology of SSc. TGF-beta regulates diverse biological activities including cell growth, cell death or apoptosis, cell differentiation, and extracellular matrix synthesis. TGF-beta is known to induce the expression of extracellular matrix proteins in mesenchymal cells and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the extracellular matrix. This review focuses on the possible role of autocrine TGF-beta signaling in the pathogenesis of SSc.

Epidermal growth factor up-regulates transforming growth factor-beta receptor type II in human dermal fibroblasts via p38 mitogen-activated protein kinase pathway

TGF-beta receptors (TbetaRs) are serine/threonine kinase receptors that bind to TGF-beta and propagate intracellular signaling through Smad proteins. TbetaRs are repressed in some human cancers and expressed at high levels in several fibrotic diseases. We demonstrated that epidermal growth factor (EGF) up-regulates type II TGF-beta receptor (TbetaRII) expression in human dermal fibroblasts. EGF-mediated induction of TbetaRII expression was inhibited by the treatment of fibroblasts with a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, whereas MEK inhibitor PD98059 did not block the up-regulation of TbetaRII by EGF. EGF induced the TbetaRII promoter activity, and this induction was significantly blocked by SB203580, but not by PD98059. The overexpression of the dominant negative form of p38alpha or p38beta significantly reduced the induction of TbetaRII promoter activity by EGF. These results indicate that the EGF-mediated induction of TbetaRII expression involves the p38 MAPK signaling pathway. The EGF-mediated induction of TbetaRII expression may participate in a synergistic interplay between EGF and TGF-beta signaling pathway.

Increased expression of integrin alpha(v)beta3 contributes to the establishment of autocrine TGF-beta signaling in scleroderma fibroblasts

The constitutive secretion of latent TGF-beta by many cell types in culture suggests that extracellular mechanisms to control the activity of this potent cytokine are important in the pathogenesis of the diseases in which this cytokine may be involved, including fibrotic disorders. In this study, we focused on the alpha(v)beta3 integrin, which is recently demonstrated to function as an active receptor for latent TGF-beta1 through its interaction with latency-associated peptide-beta1, and investigated the involvement of this integrin in the pathogenesis of scleroderma. Scleroderma fibroblasts exhibited increased alpha(v)beta3 expression compared with normal fibroblasts in vivo and in vitro. In scleroderma fibroblasts, ERK pathway was constitutively activated and such abnormality induced the up-regulation of alpha(v)beta3. Transient overexpression of alpha(v)beta3 in normal fibroblasts induced the increase in the promoter activity of human alpha2(I) collagen gene and the decrease in that of human MMP-1 gene. These effects of alpha(v)beta3 were almost completely abolished by the treatment with anti-TGF-beta Ab or TGF-beta1 antisense oligonucleotide. Furthermore, the addition of anti-alpha(v)beta3) Ab reversed the expression of type I procollagen protein and MMP-1 protein, the promoter activity of human alpha2(I) collagen gene, and the myofibroblastic phenotype in scleroderma fibroblasts. These results suggest that the up-regulated expression of alpha(v)beta3 contributes to the establishment of autocrine TGF-beta loop in scleroderma fibroblasts, and this integrin is a potent target for the treatment of scleroderma.

Recombinant human anti–transforming growth factor β1 antibody therapy in systemic sclerosis: A multicenter, randomized, placebo-controlled phase I/II trial of CAT-192

OBJECTIVE

To evaluate CAT-192, a recombinant human antibody that neutralizes transforming growth factor beta1 (TGFbeta1), in the treatment of early-stage diffuse cutaneous systemic sclerosis (dcSSc).

METHODS

Patients with SSc duration of <18 months were randomly assigned to the placebo group or to 1 of 3 CAT-192 treatment groups: 10 mg/kg, 5 mg/kg, 0.5 mg/kg. Infusions were given on day 0 and weeks 6, 12, and 18. The primary objective of this study was to evaluate the safety, tolerability, and pharmacokinetics of CAT-192. Secondary outcomes included the modified Rodnan skin thickness score (MRSS), the Scleroderma Health Assessment Questionnaire, assessment of organ-based disease, serum levels of soluble interleukin-2 receptor, collagen propeptides (N propeptide of type I [PINP] and type III collagen), and tissue levels of messenger RNA for procollagens I and III and for TGFbeta1 and TGFbeta2.

RESULTS

Forty-five patients were enrolled. There was significant morbidity and mortality, including 1 death in the group receiving 0.5 mg/kg of CAT-192 and 3 deaths in the group receiving 5 mg/kg of CAT-192. There were more adverse events and more serious adverse events in patients receiving CAT-192 than in those receiving placebo, although these events were not more frequent in the high-dose treatment group. The MRSS improved in all groups during the study, but there was no evidence of a treatment effect for CAT-192. Improvement in the MRSS correlated with the disease duration (r = -0.54, P = 0.0008). Changes in the PINP level from baseline correlated with changes in the MRSS (r = 0.37, P = 0.027).

CONCLUSION

We report the first evaluation of a systemically administered and repeatedly dosed anti-TGFbeta1 drug. In this pilot study, CAT-192, in doses up to 10 mg/kg, showed no evidence of efficacy. The utility of clinical and biochemical outcome measures and the feasibility of multicenter trials of early dcSSc were confirmed.

Constitutively phosphorylated Smad3 interacts with Sp1 and p300 in scleroderma fibroblasts

OBJECTIVE

To elucidate the role of transforming growth factor-beta (TGF-beta)/Smad signalling in the increased expression of the collagen gene in systemic sclerosis (SSc) fibroblasts.

METHODS

Dermal fibroblasts from seven patients with diffuse SSc of recent onset and from seven healthy individuals were studied. The expression levels of Smad2, Smad3 and Smad4 proteins were determined by immunoblotting. Smad3 phosphorylation and the interaction of Smad3 with Sp1 or p300 were analysed using immunoprecipitation. The effects of overexpression of Smad proteins or Sp1 on the human alpha2(I) collagen gene transcription were investigated with chloramphenicol acetyltransferase (CAT) assays using the -772 COL1A2/CAT construct.

RESULTS

Constitutive increased Smad3 phosphorylation was detected in SSc fibroblasts compared with normal fibroblasts. Increased interaction of Smad3 with Sp1 as well as p300 was also detected in SSc fibroblasts. The overexpression of Smad3 caused an increase of up to 5-fold in COL1A2 promoter activity in normal fibroblasts, while Smad3 caused a small increase in COL1A2 promoter activity in SSc fibroblasts. However, neither Smad2 nor Smad4 caused significant effects in COL1A2 promoter activity in normal fibroblasts or SSc fibroblasts. The overexpression of Sp1 caused further increase in COL1A2 promoter activity stimulated by TGF-beta in normal fibroblasts, but did not change COL1A2 promoter activity in the presence of TGF-beta in SSc fibroblasts. The combined overexpression of Smad3 and Sp1 significantly enhanced TGF-beta response in normal fibroblasts, but less markedly in SSc fibroblasts.

CONCLUSIONS

These results suggested that SSc fibroblasts are less sensitive to exogenous TGF-beta stimulation because they are already activated by the autocrine TGF-beta loop.

Involvement of alphavbeta5 integrin-mediated activation of latent transforming growth factor beta1 in autocrine transforming growth factor beta signaling in systemic sclerosis fibroblasts

OBJECTIVE

To confirm the involvement of alphavbeta5 in the self-activation system in systemic sclerosis (SSc) fibroblasts.

METHODS

Levels of alphavbeta5 expression were analyzed by immunoprecipitation. The promoter activity of the human alpha2(I) collagen gene was determined by transient transfection assay. Phosphorylation levels and DNA binding ability of Smad3 were investigated by immunoprecipitation and DNA affinity precipitation, respectively. The localization of active transforming growth factor beta (TGFbeta) was determined by coculture assay using TMLC cells (mink lung epithelial reporter cells that stably express a portion of the plasminogen activator inhibitor 1 promoter). The morphologic features of cells were determined by immunofluorescence analysis.

RESULTS

Levels of alphavbeta5 expression were significantly elevated in SSc fibroblasts compared with normal fibroblasts. Treatment with anti-alphavbeta5 antibody or beta5 antisense oligonucleotide significantly reduced human alpha2(I) collagen gene promoter activity in SSc fibroblasts. In SSc fibroblasts pretreated with TGFbeta1 antisense oligonucleotide, the exogenous latent TGFbeta1 stimulation significantly increased human alpha2(I) collagen gene promoter activity; this effect was significantly reduced in the presence of anti-alphavbeta5 antibody. Phosphorylation levels and DNA binding ability of Smad3 in SSc fibroblasts were significantly reduced by treatment with beta5 antisense oligonucleotide. The luciferase activity of TMLC cells cocultured with SSc fibroblasts was significantly elevated compared with that of TMLC cells cocultured with normal fibroblasts and was significantly reduced in the presence of anti-alphavbeta5 antibody. Anti-alphavbeta5 antibody reversed the myofibroblastic features of SSc fibroblasts.

CONCLUSION

Up-regulated expression of alphavbeta5 contributes to the establishment of autocrine TGFbeta signaling in SSc fibroblasts through activation of endogenous latent TGFbeta1.

Scleroderma, fibroblasts, signaling, and excessive extracellular matrix

Excessive extracellular matrix (ECM) deposition in the skin, lung, and other organs is a hallmark of systemic sclerosis (SSc). The pathogenesis of SSc is still poorly understood, but increasing evidence suggests that various cytokines such as transforming growth factor (TGF)-beta and their signaling pathways are key mediators of tissue fibrosis as a consequence of ECM accumulation in the pathogenesis of fibrosis such as SSc. TGF-beta regulates diverse biologic activities including cell growth, cell death or apoptosis, cell differentiation, and ECM synthesis. TGF-beta is known to induce the expression of ECM proteins in mesenchymal cells, and to stimulate the production of protease inhibitors that prevent enzymatic breakdown of the ECM. This paper focuses on the possible role of ECM, various cytokines, especially TGF-beta signal transduction pathways in the pathogenesis of fibrosis in SSc.

Increased Phosphorylation and Activation of Mitogen-Activated Protein Kinase p38 in Scleroderma Fibroblasts

Transforming growth factor-beta (TGF-beta) stimulates the transcription of the alpha2(I) collagen gene. The dermal fibroblast activation in systemic sclerosis (SSc) may be a result of stimulation by autocrine TGF-beta. In this study, we investigated whether p38 mitogen-activated protein kinase (MAPK) is involved in TGF-beta-induced transcriptional activation of the human alpha2(I) collagen gene in normal dermal fibroblasts and in upregulated extracellular matrix (ECM) expression in SSc fibroblasts. Type I collagen expression induced by TGF-beta was suppressed by the specific p38 MAPK inhibitors SB203580 or SB202190 in normal fibroblasts. TGF-beta induced phosphorylation and activation of p38 MAPK in normal dermal fibroblasts. Transient transfection of dominant-negative mutant p38 MAPK into normal fibroblasts abolished TGF-beta-induced promoter activity of the human alpha2(I) collagen gene in normal fibroblasts. Moreover, constitutive phosphorylation and activation of p38 MAPK was demonstrated in SSc fibroblasts, and the inhibition of p38 MAPK using specific p38 MAPK inhibitors or dominant-negative mutant p38 MAPK abolished the upregulated expression of type I collagen or fibronectin in SSc fibroblasts. These results strongly suggest the contribution of p38 MAPK signaling to the TGF-beta-mediated regulation of the human alpha2(I) collagen gene in normal dermal fibroblasts and constitutive upregulated expression of type I collagen and fibronectin in SSc fibroblasts.

Activation of Key Profibrotic Mechanisms in Transgenic Fibroblasts Expressing Kinase-deficient Type II Transforming Growth Factor-β Receptor (TβRIIΔk)

We have generated transgenic mice expressing a kinase-deficient type II transforming growth factor-beta (TGFbeta) receptor selectively on fibroblasts (TbetaRIIDeltak-fib). These mice develop dermal and pulmonary fibrosis. In the present study we explore activation of TGFbeta signaling pathways in this strain and examine the profibrotic properties of explanted transgenic fibroblasts including myofibroblast differentiation and abnormal metalloproteinase production. Gene expression profiles of littermate wild type or transgenic fibroblasts were compared using high-density gene arrays and validated by Taqman reverse transcriptase-PCR, Northern and Western blotting. Using a specific inhibitor (SD-208) we demonstrate that the abnormal phenotype of these cells is dependent upon TbetaRI kinase (ALK5) activity, and that transgenic fibroblasts show enhanced expression and activation of TGFbeta together with increased levels of wild type TbetaRII. Moreover, we confirm that transgene expression is itself regulated by TGFbeta and that expression at low levels facilitates signaling, whereas high level expression is inhibitory. For a subset of TGFbeta responsive genes basal up-regulation is normalized or suppressed by exogenous recombinant TGFbeta1 at time points coincident with increased transgene expression. These findings explain the profound refractoriness of TbetaRIIDeltak-fib fibroblasts to exogenous TGFbeta1, despite their activated phenotype. Thus, transgenic fibroblasts recapitulate many hallmark biochemical properties of fibrotic cells, including high level CTGF (CCN2) expression and type I collagen overproduction, altered MMP production, and myofibroblast differentiation. These cells also show an enhanced ability to contract collagen gel matrices. Our study demonstrates that altered high affinity TGFbeta receptor function may lead to ligand-dependent activation of downstream signaling, and provides further evidence of a pivotal role for sustained TGFbeta overactivity in fibrosis.

Differential effects of the immunosuppressant FK-506 on human ?2(I) collagen gene expression and transforming growth factor ? signaling in normal and scleroderma fibroblasts

OBJECTIVE

To investigate the effects of FK-506 on the expression of the human alpha2(I) collagen gene and transforming growth factor beta (TGFbeta) signaling in normal and scleroderma fibroblasts.

METHODS

The expression levels of type I procollagen protein and alpha2(I) collagen messenger RNA (mRNA) were analyzed by immunoblotting and Northern blotting, respectively. The promoter activities of alpha2(I) collagen gene and 3TP-Lux were determined by transient transfection assay. Interaction between TGFbeta receptor type I and FK-506 binding protein 12 (FKBP12) was evaluated by immunoprecipitation.

RESULTS

FK-506 did not affect the basal expression of type I procollagen protein or alpha2(I) collagen mRNA, but it significantly reduced the TGFbeta1-induced expression of type I procollagen protein and alpha2(I) collagen mRNA in normal fibroblasts. The effect of FK-506 was regulated posttranscriptionally, but not transcriptionally. In scleroderma fibroblasts, FK-506 significantly reduced the expression of type I procollagen protein and alpha2(I) collagen mRNA through posttranscriptional regulation, but not transcriptional regulation. FK-506 increased the basal activity of the 3TP-Lux promoter, but it did not affect the TGFbeta1-induced promoter activity in normal fibroblasts. In contrast, FK-506 did not affect the basal or the TGFbeta1-induced 3TP-Lux promoter activity in scleroderma fibroblasts. Furthermore, FKBP12, which protects TGFbeta receptor type I from ligand-independent activation by TGFbeta receptor type II, constitutively dissociated from TGFbeta receptor type I in scleroderma fibroblasts.

CONCLUSION

FK-506 inhibits alpha2(I) collagen gene expression by reducing the stability of mRNA without exhibiting its activation effect on TGFbeta signaling in scleroderma fibroblasts.

Recent advances in fibroblast signaling and biology in scleroderma

PURPOSE OF REVIEW

Systemic sclerosis is a complex disease manifesting itself by fibrosis of skin and other internal organs. Fibroblasts isolated from scleroderma lesions and cultured in vitro are characterized by increased synthesis of collagen and other extracellular matrix proteins, consistent with the disease phenotype. Cultured systemic sclerosis fibroblasts therefore serve as a principal experimental model for studying the molecular and cellular mechanisms involved in collagen overproduction in this disease. This review will discuss recent findings related to intracellular signal transduction pathways implicated in deregulated extracellular matrix deposition by systemic sclerosis fibroblasts.

RECENT FINDINGS

Recent findings suggest that constitutively elevated synthesis of extracellular matrix by cultured systemic sclerosis fibroblasts is, at least in part, due to the aberrant activation of the autocrine transforming growth factor-beta signaling. Enhanced constitutive transforming growth factor-beta signaling may result from the elevated levels of transforming growth factor-beta receptor type I and/or inappropriate activation of Smad3. These alterations of the transforming growth factor-beta signaling in systemic sclerosis fibroblasts may facilitate increased collagen production in vivo even under conditions of low ligand availability. However, there exist many inconsistencies among published reports regarding the detailed mechanisms of this pathway in systemic sclerosis fibroblasts, and additional studies in this area are needed. Other signaling molecules implicated in fibrotic phenotype include several members of the protein kinase C family, mammalian target of rapamycin, mitogen-activated protein kinase, necdin, reactive oxygen species, and sphingolipids. These signaling pathways may work in conjunction with transforming growth factor-beta signaling to regulate the behavior of systemic sclerosis fibroblasts.

SUMMARY

Alterations in multiple signaling pathways contribute to elevated extracellular matrix synthesis by systemic sclerosis fibroblasts. Improved understanding of the key signaling molecules may provide a novel avenue for therapeutic interventions.

Phosphatidylinositol 3-kinase is involved in alpha2(I) collagen gene expression in normal and scleroderma fibroblasts

TGF-beta is implicated in the pathogenesis of fibrotic disorders. It has been shown that Smad3 promotes the human alpha2(I) collagen (COL1A2) gene expression by TGF-beta1 in human dermal fibroblasts. Here, we investigated the role of phosphatidylinositol 3-kinase (PI3K) in the COL1A2 gene expression in normal and scleroderma fibroblasts. In normal fibroblasts, the PI3K inhibitor, LY294002, significantly decreased the basal and the TGF-beta1-induced increased stability of COL1A2 mRNA. The TGF-beta1-induced COL1A2 promoter activity, but not the basal activity, was significantly attenuated by LY294002 or the dominant negative mutant of p85 subunit of PI3K, while the constitutive active mutant of p110 subunit of PI3K did not affect the basal or the TGF-beta1-induced COL1A2 promoter activity. LY294002 significantly decreased the phosphorylation of Smad3 induced by TGF-beta1. Furthermore, the transient overexpression of 2xFYVE, which induces the mislocalization of FYVE domain proteins, decreased the TGF-beta1-induced Smad3 phosphorylation to a similar extent to LY294002. In scleroderma fibroblasts, the blockade of PI3K significantly decreased the mRNA stability and the promoter activity of the COL1A2 gene. Furthermore, LY294002 and the transient overexpression of 2xFYVE completely diminished the constitutive phosphorylation of Smad3. These results indicate that 1) the basal activity of PI3K is necessary for the COL1A2 mRNA stabilization in normal and scleroderma fibroblasts, 2) there is an unidentified FYVE domain protein specifically interacting with Smad3, and 3) the basal activity of PI3K and the FYVE domain protein are indispensable for the efficient TGF-beta/Smad3 signaling in normal fibroblasts and for the establishment of the constitutive activation of TGF-beta/Smad3 signaling in scleroderma fibroblasts.

Antifibrotic therapy in scleroderma: extracellular or intracellular targeting of activated fibroblasts?

Therapeutic anticytokine approaches have revolutionized the treatment of chronic inflammatory diseases, and targeting of transforming growth factor-beta (TGF-beta), a key factor in the pathogenesis of fibrosis, is undergoing evaluation for scleroderma. Several considerations dictate a cautious approach to anti-TGF-beta interventions. These include the possibility of multiple cytokines having overlapping roles in the pathogenesis of fibrosis and concerns that, in light of its numerous homeostatic functions, blocking TGF-beta may have serious adverse consequences. Furthermore, as autonomously activated cells, scleroderma fibroblasts may be unresponsive to blockade of TGF-beta signaling. This article reviews the experimental evidence underlying these concerns, and indicates rational approaches to addressing and overcoming them.

Cytokine regulation of pulmonary fibrosis in scleroderma

Pulmonary fibrosis occurs in up to 70% of scleroderma patients and progresses to cause severe restrictive lung disease in about 15% of patients. The mechanisms that cause pulmonary fibrosis in scleroderma remain incompletely understood. Increased amounts of mRNA or protein for multiple profibrotic cytokines and chemokines have been identified in lung tissue or broncholveolar lavage samples from scleroderma patients, when compared to healthy controls. These cytokines include transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), oncostatin M (OSM), monocyte chemotactic factor-1 and pulmonary and activation-regulated chemokine (PARC). Potential cellular sources of these profibrotic cytokines and chemokines in scleroderma lung disease include alternatively activated macrophages, activated CD8+ T cells, eosinophils, mast cells, epithelial cells and fibroblasts themselves. This review summarizes the literature on involvement of cytokines and chemokines in the development of pulmonary fibrosis in scleroderma.

The role of chemokines in the pathogenesis of scleroderma

PURPOSE OF REVIEW

The triad of pathologic changes that defines systemic sclerosis (scleroderma) includes immune system activation with autoimmunity; an obliterative, proliferative small vessel vasculopathy; and fibrosis. Available data suggest that several cytokines, including chemokines, contribute to the development of scleroderma complications. This review focuses on chemokines and their contribution to tissue fibrosis and pulmonary hypertension in scleroderma.

RECENT FINDINGS

Proteins and mRNAs for monocyte chemoattractant protein-1; pulmonary and activation-regulated chemokine; macrophage inflammatory protein-1, regulated upon activation normal T cell expressed and secreted; interleukin-8; and transforming growth factor-beta have been found in increased amounts in blood or involved tissue from scleroderma patients. These factors are likely to contribute directly to tissue damage in scleroderma through several pathways, including stimulation of extracellular matrix production, induction of TGF-beta production and activation, and chemoattraction of T cells and nonspecific inflammatory cells into tissues.

SUMMARY

Multiple chemokines are part of the pathologic network that causes tissue damage in scleroderma, and, as such, may provide therapeutic targets in scleroderma.

Fibroblast-specific expression of a kinase-deficient type II transforming growth factor beta (TGFbeta) receptor leads to paradoxical activation of TGFbeta signaling pathways with fibrosis in transgenic mice

To better understand the role of disrupted transforming growth factor beta (TGFbeta) signaling in fibrosis, we have selectively expressed a kinase-deficient human type II TGFbeta receptor (TbetaRIIDeltak) in fibroblasts of transgenic mice, using a lineage-specific expression cassette subcloned from the pro-alpha2(I) collagen gene. Surprisingly, despite previous studies that characterized TbetaRIIDeltak as a dominant negative inhibitor of TGFbeta signaling, adult mice expressing this construct demonstrated TGFbeta overactivity and developed dermal and pulmonary fibrosis. Compared with wild type cells, transgenic fibroblasts proliferated more rapidly, produced more extracellular matrix, and showed increased expression of key markers of TGFbeta activation, including plasminogen activator inhibitor-1, connective tissue growth factor, Smad3, Smad4, and Smad7. Smad2/3 phosphorylation was increased in transgenic fibroblasts. Overall, the gene expression profile of explanted transgenic fibroblasts using cDNA microarrays was very similar to that of littermate wild type cells treated with recombinant TGFbeta1. Despite basal up-regulation of TGFbeta signaling pathways, transgenic fibroblasts were relatively refractory to further stimulation with TGFbeta1. Thus, responsiveness of endogenous genes to TGFbeta was reduced, and TGFbeta-regulated promoter-reporter constructs transiently transfected into transgenic fibroblasts showed little activation by recombinant TGFbeta1. Responsiveness was partially restored by overexpression of wild type type II TGFbeta receptors. Activation of MAPK pathways by recombinant TGFbeta1 appeared to be less perturbed than Smad-dependent signaling. Our results show that expression of TbetaRIIDeltak selectively in fibroblasts leads to paradoxical ligand-dependent activation of downstream signaling pathways and causes skin and lung fibrosis. As well as confirming the potential for nonsignaling receptors to regulate TGFbeta activity, these findings support a direct role for perturbed TGFbeta signaling in fibrosis and provide a novel genetically determined animal model of fibrotic disease.

Epidermal growth factor up-regulates expression of transforming growth factor beta receptor type II in human dermal fibroblasts by phosphoinositide 3-kinase/Akt signaling pathway: Resistance to epidermal growth factor stimulation in scleroderma fibroblasts

OBJECTIVE

Transforming growth factor beta receptors (TGFbetaRs) are known to be expressed at high levels in several fibrotic diseases, including systemic sclerosis. In the present study, we investigated the mechanism of up-regulation of TGFbetaR expression.

METHODS

The levels of expression of TGFbetaR type II (TGFbetaRII) messenger RNA (mRNA), with or without stimulation by epidermal growth factor (EGF), were evaluated by Northern blot analysis, and the protein levels were determined by immunoblotting. The transcription activity of the TGFbetaRII gene was examined with luciferase assays using the -1670/+35 TGFbetaRII promoter luciferase construct.

RESULTS

EGF up-regulates the expression of TGFbetaRII mRNA and protein in human dermal fibroblasts. Actinomycin D, an RNA synthesis inhibitor, significantly blocked the EGF-mediated up-regulation of TGFbetaRII mRNA expression, whereas cycloheximide, a protein synthesis inhibitor, did not block this up-regulation. In addition, EGF treatment did not significantly affect the TGFbetaRII mRNA half-life. EGF-mediated induction of TGFbetaRII expression was inhibited by treatment of fibroblasts with the selective phosphoinositide 3-kinase (PI 3-kinase) inhibitors wortmannin or LY294002, and Akt inhibitor also blocked EGF-induced expression of TGFbetaRII. In addition, EGF induced TGFbetaRII promoter activity, and this induction was significantly blocked by wortmannin, LY294002, or Akt inhibitor. Cotransfection with a dominant-negative mutant of p85 (the regulatory component of PI 3-kinase) or Akt significantly reduced the induction of TGFbetaRII promoter activity by EGF. Moreover, a constitutive active form of p110 (a catalytic component of PI 3-kinase) induced TGFbetaRII promoter activity. In addition, scleroderma fibroblasts expressed increased levels of TGFbetaRII but did not show further up-regulation of TGFbetaRII expression by EGF.

CONCLUSION

These results indicate that EGF-mediated induction of TGFbetaRII expression occurs at the transcription level, does not require de novo protein synthesis, and involves the PI 3-kinase/Akt signaling pathway, and that abnormal activation of EGF-mediated signaling pathways, including PI 3-kinase or Akt, might play a role in the up-regulation of TGFbetaRII in scleroderma fibroblasts.